Hypex Ncore

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At nominal listening level my DACs S/N ratio appears to be poor. So i want to be able to raise its signal level by keeping a higher level from the DAC. This would mean i have to drop the gain on the NC400 and UcD400HxR modules connected to the speaker drivers in my active setup.

Is this a safe enough operation to try? I know there are some mentions in the thread. But has any one made these mods successfully? Any pointers are appreciated.

Why not check first where the poor S/N ratio of your DAC comes from? A good DAC should have good enough S/N ratio not to raise noise levels further up the chain.
 
thanks Antana/Julf, i was able to locate the resistor and saw some pictures of their location on the UcD400. Removing seems feasible, replacement would be harder.

Pieter, Yes that is a fair point. But at listenable levels i have quite a bit of digital volume attenuation. This is where a slightly lowered gain from these powerful modules would help.

I think it is a bit more complicated, my midrange driver is low sensitivity at 85db and tweeter is 91db. So i have that 6db level down on my tweeter. Also with that low sensitivity midrange, lowering the power amp gain might not be a great idea.

I have to think this through before making any changes. Any advice is always appreciated.
 
ummm...

At nominal listening level my DACs S/N ratio appears to be poor. So i want to be able to raise its signal level by keeping a higher level from the DAC. This would mean i have to drop the gain on the NC400 and UcD400HxR modules connected to the speaker drivers in my active setup.

Is this a safe enough operation to try? I know there are some mentions in the thread. But has any one made these mods successfully? Any pointers are appreciated.

I am not sure I understand? If you raise the gain of your DAC, you will also increase its noise floor, as the noise floor is almost certainly that of its analog output stage. If you need to lower the noise floor of the system, what you would want to do is to lower the gain of the DAC, and then raise the gain of the nCore (if you even need that much gain).
 
So i have that 6db level down on my tweeter. Also with that low sensitivity midrange, lowering the power amp gain might not be a great idea.

If the difference is only 6 dB, I wouldn't bother with changing the gain of the amps. In any case, you can always try with a simple 2-resistor attenuator (or pot) to see if lowering the gain solves your noise level issue.
 
Most likely the noise comes from the analog output stage of the DAC.
Digital attenuation before the analog output stage of the DAC does not help but worsen things.
When DAC, crossover and amplifiers have good S/N ratios there is enough room to balance the system without being faced with noise problems.
Too much noise at the source, the case here, is the worst place. Improving the S/N of the DAC output stage is the only way to solve the problem.
He could also skip digital attenuation for volume control. Then the DAC will have normal unattenuated output (and best S/N ratio) and try a good normal volume control between DAC and active crossover. That migh solve the noise problem, and I would not be surprised if that would give a better sound quality as well (I am not so fond of digital attenuators).
 
Most likely the noise comes from the analog output stage of the DAC.

Indeed.

Too much noise at the source, the case here, is the worst place. Improving the S/N of the DAC output stage is the only way to solve the problem.
And one way to improve it is by turning up the digital volume control (and lowering the gain in the subsequent amp, either by modifying the feedback reistors or by passively attenuating the signal).

I would not be surprised if that would give a better sound quality as well (I am not so fond of digital attenuators).
Do you have any rational reason for your dislike of digital attenuators?
 
And one way to improve it is by turning up the digital volume control (and lowering the gain in the subsequent amp, either by modifying the feedback reistors or by passively attenuating the signal).

The right place to lower the gain would be the gain control of the active crossover; no need to modify feedback resistors in the amp or add additional attenuators.
 
The right place to lower the gain would be the gain control of the active crossover; no need to modify feedback resistors in the amp or add additional attenuators.

I don't quite follow your logic. To reduce noise, you have to increase the gain in the crossover (assuming the noise is coming from the analog stage of the DAC in the crossover), and that has to be compensated in the amp.
 
To my ears ( and that is rational enough for me) digital attenuators blur transparency when attenuating.

OK, so basically subjective opinion. Of course a totally valid reason for you personally, but not very helpful to anyone else. I assume you haven't done any double-blind comparisons under controlled conditions?

We can argue about the validity of subjective perceptions until the cows come home, but I had hoped for some sort of technical reasoning.
 
I don't quite follow your logic. To reduce noise, you have to increase the gain in the crossover (assuming the noise is coming from the analog stage of the DAC in the crossover), and that has to be compensated in the amp.

The logic is rather simple IME: when the DAC has standard output (2 VRMS) and acceptable S/N ratio there would be no noise issues. Some quality kind of volume control between DAC and active crossover.
I presume that the source (DAC) has enough output for the rest of the system.
Normal active crossovers have gain controls, mostly in the feedback loops of opamp circuits. Sometimes additional gain can be done there, but preferably only attenuation when there is enough signal. That is the right place to balance the system in case of multi-way.
Doing it by changing the gain of power amps is much more complex and less flexible.
 
OK, so basically subjective opinion. Of course a totally valid reason for you personally, but not very helpful to anyone else. I assume you haven't done any double-blind comparisons under controlled conditions?

We can argue about the validity of subjective perceptions until the cows come home, but I had hoped for some sort of technical reasoning.

There has been discussion on the technical side of things here and there, but, as usual, these discussions are fruitless most of the time.
It seems there are three camps within the audiophile community:
- those who can only "enjoy" their gear knowing the specs are "great"; let's call them techno-audiophiles (mostly less involved in music itself, sitting nervously in front of the speakers "waiting" for a "mistake" in the reproduction....not the happiest listeners but often spending a lot of cash and continuously looking for "better");
- those who don't care about specs; they only care for "tone", "emotion"; technical shortcomings don't prevent them from enjoying;
- a "middle" group: those who look for good reproduction of music based on technical sound equipment.
Subjectivism is king, double-blind comparisons under controlled conditions will never replace subjectivism in audio because people are too different in their preferences and approaches, and IMO it is better so.
 
The logic is rather simple IME: when the DAC has standard output (2 VRMS) and acceptable S/N ratio there would be no noise issues. Some quality kind of volume control between DAC and active crossover.
I presume that the source (DAC) has enough output for the rest of the system.

OK, I see - you are assuming the noise comes from the DAC *before* the crossover, I am assuming it comes from the DAC *after* the crossover.

Normal active crossovers have gain controls, mostly in the feedback loops of opamp circuits.
By "active crossover" I tend to assume digital crossovers these days.
 
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